1. Field of the Invention
The invention relates in general to a wireless communication apparatus and method.
2. Description of the Related Art
Wireless communication apparatuses are products that modern people cannot live without in daily lives. Everyday countless numbers of wireless audios and data communication support operations of the modern lifestyle. Mobile communication bandwidths that people demand also increasingly expand as technologies continue to progress. In an era of the second-generation (2G) communication technology, the communication bandwidth falls at a level of approximately 100 Kbps. Having entered an era of the third-generation (3G) communication technology, the communication bandwidth had improved for about 100 times. Having entered an era of the fourth-generation (4G) communication technology, it is estimated that the communication bandwidth be similarly improved for about 100 times to reach a level of 1000 Mbsp, or 1 Gpbs.
With the immense demand on communication bandwidths, a considerable wireless communication frequency range is inevitably occupied regardless of the type of physical-layer communication technologies applied. Although theoretically feasible, communication frequencies of nations around the globe have long been divided and designated for various kinds of communication applications. Thus, no continuous wireless communication frequencies in such large range can be found when deploying a new generation wireless communication network. In a situation where frequencies currently with occupants cannot be released for other uses, a technology called carrier aggregation (CA) needs to be utilized.
Despite that no continuous frequencies are available for communication, carrier aggregation provides a communication capability by aggregating different carriers in multiple wavebands. FIG. 1A shows a frequency diagram of multiple wavebands including carriers having different frequencies. In FIG. 1A, the horizontal axis represents wireless communication frequencies. These wireless communication frequencies include multiple usable wavebands, e.g., a first waveband 110 and a second waveband 120 in FIG. 1A. The bandwidths of these wavebands are not necessarily the same, and the wavebands may be continuous or non-continuous wavebands. As shown in FIG. 1A, the first waveband 110 and the second waveband 120 are non-continuous.
The first waveband 110 may include multiple unoccupied carrier frequencies, e.g., a carrier A 112 and a carrier B 114. The carrier A 112 and the carrier B 114 in FIG. 1A are continuous, and may have different bandwidths. For example, the bandwidth of the carrier B 114 in FIG. 1A is larger than the bandwidth of the carrier A 112. The second waveband 120 may also include multiple usable carrier frequencies, e.g., a carrier C 122 and a carrier D 124. The bandwidth of the carrier C 122 may be different from or the same as the bandwidth of the carrier D 124. A wireless communication apparatus that does not support carrier aggregation can only select one from the four carriers for communication while being incapable of utilizing the remaining three carriers.
FIG. 1B shows a frequency diagram of type 1 of carrier aggregation. A wireless communication apparatus that supports such type 1 of carrier aggregation is capable of aggregating multiple continuous carriers located in the first waveband 110, e.g., the carrier A 112 and the carrier B 114, into a communication channel. Such type of carrier aggregation is referred to as intra-band carrier aggregation with continuous component carriers. The carrier A 112 and the carrier B 114 that are aggregated are referred to as component carriers (CCs).
FIG. 1C shows a frequency diagram of type 2 of carrier aggregation. A wireless communication apparatus that supports such type 2 of carrier aggregation is capable of aggregating multiple non-continuous carriers located in the second waveband 120, e.g., the carrier C 122 and the carrier D 124, into a communication channel. Such type of carrier aggregation is referred to as intra-band carrier aggregation with non-continuous component carriers. Similarly, the carrier C 122 and the carrier D 124 that are aggregated are referred to as component carriers.
FIG. 1D shows a frequency diagram of type 3 and type 4 of carrier aggregation. The type 3 of carrier aggregation aggregates the carrier A 112 and the carrier B 114 in the first waveband 110, and the carrier C 122 in the second waveband 120. The type 4 of carrier aggregation aggregates the carrier A 112 and the carrier B 114 in the first waveband 110, and at the carrier C 122 and the carrier D 124 in the second waveband 120. These two types of carrier aggregation are referred to as inter-band carrier aggregation with non-continuous component carriers.
Among the four exemplary types of carrier aggregation, apart from the intra-band carrier aggregation with continuous component carriers, the other three types of carrier aggregation with non-continuous component carriers can only be handled by multiple transceivers. These transceivers, or referred to as a radio-frequency (RF) chain, commonly refers to signal circuits other than a baseband processor, and may include components or a combination of antennas, mixers, oscillators, amplifiers and delay circuits.
In the example of type 2 shown in FIG. 1C, the carrier C 122 and the carrier D 124 are non-continuous and are spaced by non-carrier frequencies. If this range of continuous frequencies is processed by one transceiver, the transceiver needs to spend large amounts of resources or time to remove signals of the non-carrier frequencies. In general, two transceivers are utilized to receive signals of the carrier C 122 and the carrier D 124, respectively.
Similarly, in the examples of type 3 and type 4 shown in FIG. 1D, as the component carriers are located in different wavebands, i.e., at least two component carriers are non-continuous with non-carrier frequencies in between, multiple transceivers need to be utilized to respectively handle the component carriers in the different wavebands. For example, in the example of type 3, a transceiver that processes a larger bandwidth may be utilized to handle the carrier A 112 and the carrier B 114, and another transceiver may be utilized to handle the carrier C 122. In the example of type 4, in addition to the two transceivers for type 3, a third transceiver is utilized to handle signals of the carrier D 124.
In a situation of type 1, one single transceiver that processes a larger bandwidth may be utilized to handle the carrier A 112 and the carrier B 114, or two transceivers that process smaller bandwidths may be utilized to handle the carrier A 112 and the carrier B 114, respectively. The signal quality received by transceivers that process smaller bandwidths is generally better. However, transceivers that process smaller bandwidths are flawed by occupying additional volumes as well as consuming increased costs and power consumption.
As concluded from the above description, in most types of carrier aggregation, a wireless communication apparatus needs to involve at least two transceivers in order to support carrier aggregation. In practice, when a wireless communication apparatus has activated the carrier aggregation function, it usually means that the wireless communication apparatus is currently performing high-speed transmission. Given sufficient resources to base stations and wireless carrier frequencies, a wireless communication apparatus usually activates all transceivers to perform carrier aggregation communication. However, due to the mobility of a wireless communication apparatus, good wireless channel environments to base stations with which the wireless communication apparatus communicates may not be maintained at all times. Upon entering a range of another base station that provides better services, a wireless communication apparatus needs to have the capability of learning information of another base station, so as to allow a wireless communication network to hand over signals from the original base station to another base station, and to further allow wireless communication to maintain an original bandwidth level or even yield better performance.
However, as the above wireless communication apparatus has already allotted all its transceivers to support carrier aggregation communication, the wireless communication apparatus cannot call any of the transceivers to receive information of another base station. Therefore, provided that carrier aggregation is satisfied as much as possible, there is a need for a wireless communication apparatus and method that call one of the transceivers to receive information of another base station. Similarly, for a wireless communication apparatus having multiple transceivers, even when carrier aggregation is not supported, there is also a need for a wireless communication apparatus and method that call one of the transceivers to receive information of another base station.